Maintenance & Technical > KX500 Original

93 KX 500 Rebuild

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Jeff90lx:
Thanks for the input guys,

 I found a piston guide but I can't get the thing to load for some reason... I just don't want to put this thing back together if the issue that caused it is not resolved. I will be sending the cylinder to Millennium Tech. to get re-plated and will probably go with the Wossner piston as suggested. The few people I have talked to about it say that it looks like some kind of lean condition that caused it, however from what I've read... If the bike had an air leak it would have been running funny prior to giving up the ghost. It's just weird because the bike ran great right up to the end... So I'm a little stumped  :?

sandblaster:
Do yourself a huge favor and check the crank for wear between the rod and the crank halves.
Get a feeler gauge and stick it in there as shown below:



.016" -.020" is factory new specs.
You can run the crankshaft all the way to .028" before it's reached it's service limit.
If it's out of service specs it's time for a full rebuild.

If it is good you could install the new top end.
However, if you choose to only replace the top end, either do a leak down test yourself or have a shop do it to determine your seal condition. If it won't pass a leak down test then you know it's time to replace every seal or you risk burning up your new top end.

If I were you I would disassemble the rest of the engine and at a minimum replace every, bearing, washer, snap ring, bushing, seal, and gasket possible. I would also carefully inspect the shift forks, drum, and gear dogs.
Why? Without knowing the true history of that engine and no leak down test done before it was disassembled, you have no idea what you have. You could drop some serious coin into the top end and then fry it shortly thereafter.

We have heard too many stories of guys getting frustrated and selling their K5's for scrap because they did not understand the risks of not checking a few things...

Jeff90lx:
Sandblaster,

It looks like you are in Oregon. I'm up in Washington, are there any local K5 guru's I could take it to for a full rebuild?

sandblaster:
I don't know any in Washington off the top of my head.
I'm about 2 hours south of the Washington/Oregon border in Eugene.
Some others on this site may know of someone closer..

jethrobolas:
Ha! Bought a running but clapped 93 couple years ago. Rode it twice and tore it dkwn. One ride was the purchase test. Accumulated goodies for a year.
Finished it up this spring. New tire, new wossner purchased from powerseal with replate, mains with seals, squish and compression release by Larry Wiechman, gasket and seal kit, chain and sprockets, couple trans bearings, clean and grease all chassis bearings, fresh brake juice, throttle cable, and blahblah.
Fired it up. Rolled my track cautiously. Around the track again with a bit more gusto. Open it up to run the front yard trail. Found air near my driveway on the k5 that no other bike could ever find...then skidded into a stack of a dozen utility poles laying in my yard. Hard.
Out of work for 6 weeks. Fractured tibial plateau (lucky that was all.....3 cartwheels before MY first bounce according to several of my sons buddies). New handlebars. New grips. Little tweakin' on the subframe. Sat until this October when I posted it on cl (plenty other toys).

Finally, after 4 or 5 years of talking about it, took my son to badlands ohv area and I chose the k5. Stock but fresh everything. He took my kdx200 of the same vintage. We had a blast! The k5 is no longer listed!



https://youtu.be/d0nVPqWhb28

Went from a 60 pilot to a 55. Blubbering like crazy. Video is with a 52, stock needle, clip all the way at the top. Still feels rich at small throttle and idle. Feel like i checked float level already, but winter is here and I do have a nice place to wrench on it during winter.....

Threadjack over.


Powerseal did find cracks in my transfers (I think, or maybe exhaust) but money cures almost anything.

With the proper tools, a manual, a bit of mechanical aptitude and this forum you could probably get it up to snuff with a minimum of outsourced work. Just sayin....

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